Apex domains cannot have CNAME records.
Question and response
Question
dig wpx.net. NS
Answer
wpx.net. 5 NS ns3.wpx.net.
wpx.net. 5 NS ns2.wpx.net.
wpx.net. 5 NS ns1.wpx.net.
wpx.net. 5 NS ns4.wpx.net.
Authority
The response has no authority records.
Additional
ns1.wpx.net. 5 A 194.1.147.230
ns2.wpx.net. 5 A 194.1.147.231
ns3.wpx.net. 5 A 194.1.147.210
ns4.wpx.net. 5 A 67.202.92.221
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0